import java.util.ArrayList;
import java.util.List;

public class BOke {
    public static void main(String[] args) {
        List<List<Integer>> ret=new ArrayList<>();
        List<Integer> list0=new ArrayList<>();
        List<Integer> list1=new ArrayList<>();
        ret.add(list0);
        ret.add(list1);
        list0.add(1);
        list0.add(2);
        list1.add(10);
        list1.add(20);
        System.out.println(ret.get(0));
        System.out.println(ret.get(1));
        System.out.println(ret.get(0).get(0));
        System.out.println(ret.get(0).get(1));
        System.out.println(ret.get(1).get(0));
        System.out.println(ret.get(1).get(1));
    }
}
